1. Field of the Invention
This application is based upon and claims a priority of Japanese Patent. Application No. 2007-204120, filed Aug. 6, 2007, the contents being incorporated herein by reference.
The present invention relates to the surface mounting of a vibration motor on a printed circuit board by reflow soldering.
2. Description of the Related Art
As a vibration motor of a structure suitable for surface mounting on a printed circuit board, for example, as disclosed in Japanese Patent. Publication No. 11-234943-A, there is known one having a vibration motor body attaching an eccentric weight to one end of a motor shaft, a metal holder frame provided with a motor holding part holding this vibration motor body by engagement with a motor case, and a pair of external terminal pieces attached to a plastic end cap (end bracket) sealing the opening of the motor case on the side opposite to the eccentric weight, wherein a flat bottom surface of the metal holder frame and the pair of external terminal pieces are fastened to a fastening pattern and a pair of power feed patterns of a printed circuit board by coating them with cream solder, bringing them into close contact, and reflow soldering them.
However, the above vibration motor had the following problems.
(1) In automatic mounting picking up a vibration motor and mounting it on a printed circuit board, a certain amount of deviation occurs in the positioning between the flat bottom surface of a metal holder frame and the fastening pattern or the pair of external terminal pieces and the pair of power feed patterns. In the process of melting, then cooling the cream solder for fastening by loading in an electric furnace, sometimes the axial line of the motor (center line of flat bottom surface) and center line of the fastening pattern will not be aligned and a drop in the yield will be incurred.
(2) If raising the fastening strength of the vibration motor on a printed circuit board by providing a raised bottom recess in the flat bottom surface and forming a solder reservoir there for fastening, the bottom surface of the motor case of the vibration motor will abut against the top surface of this raised bottom recess, so the degree of parallelism of the vibration motor body with respect to the flat bottom surface and fastening pattern is liable to become off.